JP4645786B2 - Exhaust gas purification catalyst - Google Patents

Exhaust gas purification catalyst Download PDF

Info

Publication number
JP4645786B2
JP4645786B2 JP2001174469A JP2001174469A JP4645786B2 JP 4645786 B2 JP4645786 B2 JP 4645786B2 JP 2001174469 A JP2001174469 A JP 2001174469A JP 2001174469 A JP2001174469 A JP 2001174469A JP 4645786 B2 JP4645786 B2 JP 4645786B2
Authority
JP
Japan
Prior art keywords
catalyst layer
catalyst
exhaust gas
agent
occlusion
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
JP2001174469A
Other languages
Japanese (ja)
Other versions
JP2002361094A (en
Inventor
哲也 渡邊
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Motors Corp
Original Assignee
Mitsubishi Motors Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mitsubishi Motors Corp filed Critical Mitsubishi Motors Corp
Priority to JP2001174469A priority Critical patent/JP4645786B2/en
Priority to KR10-2002-0028841A priority patent/KR100464715B1/en
Priority to EP20020011690 priority patent/EP1264629B1/en
Priority to DE60201707T priority patent/DE60201707T2/en
Priority to US10/163,494 priority patent/US6770590B2/en
Publication of JP2002361094A publication Critical patent/JP2002361094A/en
Application granted granted Critical
Publication of JP4645786B2 publication Critical patent/JP4645786B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
    • B01D53/945—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific catalyst
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/78—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with alkali- or alkaline earth metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/58—Platinum group metals with alkali- or alkaline earth metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/024—Multiple impregnation or coating
    • B01J37/0244—Coatings comprising several layers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Description

【０００１】
【発明の属する技術分野】
本発明は、排ガス浄化用触媒に関し、特に、耐久性および排ガス浄化性能に優れた排ガス浄化用触媒に関する。
【０００２】
【関連する背景技術】
リーンバーンエンジンや筒内噴射式エンジン等の希薄燃焼式エンジンは燃料希薄側のリーン空燃比で運転されることが多いが、リーン運転中は三元触媒の排ガス浄化作用が十分に発揮されないので、一般には、吸蔵剤が添加された触媒層をコージライト担体に担持してなるＮＯｘ吸蔵触媒が搭載される。しかしながら、ＮＯｘ吸蔵触媒、特にアルカリ金属を吸蔵剤として添加した触媒にあっては、高温下で吸蔵剤が飛散したりコージライト担体内に移動したりして吸蔵剤の量が目減りし、触媒のＮＯｘ吸蔵能力が低下するという問題が生じる。
【０００３】
このため、本出願人は、特願平１１−３７０３５８号（特開２００１−１２９４０２号公報）などにおいて触媒にゼオライトを添加することにより吸蔵剤の飛散や担体への移動を抑制することを提案している。ゼオライトに含有される珪素（Ｓｉ）は、酸性質を有してアルカリとの親和性が高いことから、アルカリ性を示す吸蔵剤を引き寄せる作用を発揮し、従って、上記提案のようにゼオライトを移動抑制剤として用いることにより吸蔵剤の飛散や移動を抑止できる。更に、Ｓｉがゼオライトとして混入されているため吸蔵剤と反応して安定物質を形成することがなく、吸蔵剤の消失ひいては触媒の吸蔵能力の低下を抑制でき、高温下での運転の後においても触媒は高いＮＯｘ吸蔵性能を維持する。
【０００４】
【発明が解決しようとする課題】
上述のようにゼオライトを添加したＮＯｘ吸蔵触媒は高温下での運転後も高いＮＯｘ吸蔵性能を維持できるが、この種の触媒においても過酷な高温下で運転した場合にはその後のＮＯｘ吸蔵性能に低下が認められ、従って高温耐久後の性能低下をより小さくした触媒の提供が要請されている。
【０００５】
そこで、この様な要請に答えるために更なる研究を進めた結果、ＮＯｘ吸蔵触媒の高温耐久後の性能低下を抑制する上で、ゼオライト自体が比較的耐熱性の低い物質であることが障害になっていることが判明した。すなわち、ゼオライトは主としてＳｉＯ２とＡｌ２Ｏ３との複合酸化物であって、高温下ではＳｉＯ２とＡｌ２Ｏ３との結合が崩れ易く、両者の結合が崩れるとＳｉＯ２またはＳｉが吸蔵剤と反応し易くなり、ＳｉＯ２またはＳｉとの反応が進んでＮＯｘ吸蔵反応に作用する吸蔵剤がその分消失し、触媒の吸蔵性能が低下する。
【０００６】
そこで、本発明は、高温耐久性に優れ、特に、過酷な高温下でのＮＯｘ吸蔵反応に作用する吸蔵剤の消失による排ガス浄化性能の悪化度合いを低減可能な排ガス浄化用触媒を提供することを目的とする。
【０００７】
【課題を解決するための手段】
請求項１に記載の発明は、担体と触媒層とを含み、この触媒層にアルカリ金属及びアルカリ土類金属からなる群から選択される少なくとも一つを吸蔵剤として添加してなる排ガス浄化用触媒において、コバルト（Ｃｏ）、ジルコニウム（Ｚｒ）、鉄（Ｆｅ）、マンガン（Ｍｎ）からなる遷移金属の群から選択される少なくとも一つの金属と珪素（Ｓｉ）とからなる複合酸化物を触媒層に混入したことを特徴とする。
【０００８】
本発明では、珪酸塩（複合酸化物中のＳｉ）は、吸蔵剤を引き寄せる作用を奏し、また、吸蔵剤との間で安定物質を生成するような化学反応を生起することがない。このため、吸蔵剤はその本来の機能すなわち吸蔵機能を失うことなくＳｉの近傍に保持され、従って触媒層における吸蔵剤の移動が抑制される。この結果、吸蔵剤の飛散や担体中へ移動した吸蔵剤と担体組成成分との化学反応による吸蔵剤の消失や吸蔵剤の硫黄被毒（燃料または排ガス中の硫黄分と吸蔵剤との反応による硫酸塩の生成）が抑制され、触媒の吸蔵性能が維持される。
【０００９】
しかも、遷移金属Ｃｏ、Ｚｒ、Ｆｅ、Ｍｎは融点が高く、これらの遷移金属とＳｉとの複合酸化物は高い熱的安定性を示す。従って、複合酸化物中のＳｉによる吸蔵剤移動抑制作用や吸蔵剤の吸蔵機能が高温下でも維持される。すなわち、遷移金属と珪素とからなる複合酸化物を触媒層に混入した触媒は熱耐久性能に優れ、高温耐久後においてもその吸蔵性能が維持される。
【００１０】
更に、請求項１に記載の発明は、触媒層の上層に、アルカリ金属及びアルカリ土類金属からなる群から選択される少なくとも一つを吸蔵剤として添加してなる第２触媒層を形成したことを特徴とする。
請求項１の発明では、第２触媒層は遷移金属と珪素とからなる複合酸化物を含まず、この第２触媒層に添加された吸蔵剤は、第２触媒層に続く触媒層に混入されている複合酸化物のＳｉによって引き寄せられる。従って、第２触媒層内の吸蔵剤の量が少なくなるため、第２触媒層ひいては全触媒層からの吸蔵剤の飛散が抑制され、触媒の吸蔵能力の低下が防止される。また、アルカリ金属やアルカリ土類金属からなる吸蔵剤はその電子供与性が強いため貴金属の酸化作用を低下させる要因になり得るが、請求項２の発明では第２触媒層内の吸蔵剤の量が少なくなるので、第２触媒層における貴金属の酸化作用低下が抑制される。すなわち、第２触媒層を触媒層上層に備えた触媒によれば、その吸蔵・浄化能力が高レベルに維持される。
【００１１】
請求項２に記載の発明は、触媒層と担体との間にアルカリ金属及びアルカリ土類金属からなる群から選択される少なくとも一つを吸蔵剤として添加してなる第２触媒層を形成したことを特徴とする。
請求項２の発明では、触媒層が触媒表面側に形成され、第２触媒層は触媒層と担体との間に形成され、第２触媒層に添加された吸蔵剤は、触媒層に含まれる複合酸化物中のＳｉによって引き寄せられる。従って、排ガスと接触し易い触媒層上層側に吸蔵剤が集まるため、排ガス空燃比をリッチ化することにより吸蔵能力を効率良く回復することができる。この様に回復効率が高いのでリッチ化に伴う燃費悪化を最小にでき、また、第２触媒層中の吸蔵剤が第２触媒層に続く触媒層へ引き寄せられるので第２触媒層における貴金属の酸化作用の低下を抑制できる。すなわち、触媒の吸蔵・浄化能力は高レベルに維持される。
【００１２】
請求項３に記載の発明は、上記触媒層の上層および上記触媒層と上記担体との間の少なくとも一方に三元触媒層を設けたことを特徴とする。
請求項３の発明では、複合酸化物中のＳｉが吸蔵剤保持作用を奏するので、三元触媒層への吸蔵剤の移動が抑制され、吸蔵剤による貴金属の酸化作用の低下が抑制され、三元触媒層ひいては触媒の浄化性能が維持される。
【００１３】
請求項４の発明では、上記複合酸化物として珪酸ジルコニウム（ＺｒＳｉＯ４）を用いたことを特徴とする。
珪酸ジルコニウムは工業的に入手し易い材料であり、従って、吸蔵剤を添加した触媒層に珪酸ジルコニウムで構成した複合酸化物を混入することにより、吸蔵剤の移動や飛散を防止するという所期の目的を安価に達成できる。
【００１４】
【発明の実施の形態】
まず、本発明の参考形態による排ガス浄化用触媒を説明する。
本参考形態の排ガス浄化用触媒は、多数のセルからなるハニカム（モノリス）型のコージライト担体を有するＮＯｘ触媒として構成されている。図１はコージライト担体の一つのセルの一部を示し、コージライト担体１０のセルは例えば四角形状に形成されている。コージライト担体１０の表面には触媒層２０が担持されている。そして、触媒層２０には、プラチナ（Ｐｔ）、パラジウム（Ｐｄ）などの貴金属と、カリウム（Ｋ）、バリウム（Ｂａ）などのＮＯｘ吸蔵剤とが添加されると共に、コバルト（Ｃｏ）、ジルコニウム（Ｚｒ）、鉄（Ｆｅ）、マンガン（Ｍｎ）からなる遷移金属の群から選択される少なくとも一つの金属と珪素（Ｓｉ）とからなる複合酸化物が混入されている。本参考形態では、この複合酸化物として珪酸ジルコニウム（ＺｒＳｉＯ４）が用いられる。
【００１５】
好ましくは、プラチナ及びパラジウムの各々の担持量を担体１リットルあたり０．１ないし１０ｇの値に設定し、カリウム及びバリウムの各々の担持量を担体１リットルあたり０．１ないし５０ｇの値に設定し、また、珪酸ジルコニウムの担持量を担体１リットルあたり０．１ないし５０ｇの値に設定する。
コージライト担体１０は、たとえば、アルミナ源の粉末、シリカ源の粉末およびマグネシア源の粉末を、アルミナ、シリカ、マグネシアの割合がコージライト組成になるように混合したものを水に分散させ、その固形分をハニカム状に成形し、このハニカム成形体を焼成したものである。
【００１６】
触媒層２０は、例えば以下のようにして、コージライト担体１０の表面に担持される。
先ず、プラチナなどの貴金属、カリウムなどのアルカリ金属、バリウムなどのアルカリ土類金属、および複合酸化物としての珪酸ジルコニウムを主成分とする粉末を含むスラリーが調製される。次いで、コージライト担体１０をスラリー中に浸漬し、これを乾燥後に焼成する。
【００１７】
以上のようにして、コージライト担体１０に触媒層２０をコーティングしてなるＮＯｘ触媒を得る。従来公知のように、このＮＯｘ触媒は、たとえば緩衝材を介してケースに収容され、希薄燃焼内燃機関の排気管内に配置される。
このＮＯｘ触媒によれば、リーン空燃比での機関運転中に排ガス中のＮＯｘが、触媒層２０に分散された触媒種の作用下で硝酸塩の形で吸蔵される。また、リッチ空燃比での機関運転中には硝酸塩が分解され、吸蔵されていたＮＯｘが窒素に還元されてＮＯｘ触媒から大気中に放出される。
【００１８】
ＮＯｘ触媒を長時間にわたって高温に晒した場合、一般には、触媒層に添加された吸蔵剤たとえばカリウムがコージライト担体中へ移動して担体中の珪素などと反応して化合物を生成し、この化合物がコージライト担体でのクラック発生要因になるが、本参考形態のＮＯｘ触媒では、触媒層２０内でのカリウムなどの吸蔵剤の移動が珪酸ジルコニウムに含まれる珪素（Ｓｉ）の近傍に保持されてコージライト担体１０への移動が阻止され、クラック発生が防止される。
【００１９】
また、吸蔵剤移動抑制作用を奏するゼオライトを触媒層に混入した触媒によれば、過酷な高温下ではその構成成分ＳｉＯ２とＡｌ２Ｏ３との結合が崩れて吸蔵剤が消失し、高温耐久後のＮＯｘ浄化効率が低下するが、本参考形態の触媒層に混入されている珪酸ジルコニウムと珪素との複合酸化物は熱的安定性が高く、複合酸化物中のＳｉによる吸蔵剤移動抑制作用は例えば８５０℃を超えるような高温下でも維持され、高温耐久後のＮＯｘ浄化効率に優れる。
【００２０】
本発明者は上記の作用、効果を確認すべく、珪酸ジルコニウムと珪素との複合酸化物を触媒層に混入させた本参考形態のＮＯｘ触媒とゼオライトを混入した従来のＮＯｘ触媒のそれぞれについて熱耐久試験後のＮＯｘ浄化効率を測定し、測定結果を図２および図３に示す。
図２は、耐久温度（熱耐久試験での触媒温度）と熱耐久試験後におけるＮＯｘ浄化効率との関係すなわち触媒の耐久温度−ＮＯｘ浄化効率特性を示す。評価温度は５００℃である。図２中、四角形マークは本参考形態の触媒の特性を示し、三角形マークは従来の触媒の特性を示し、また、破線は新品（劣化前）の触媒の特性を表している。図２からわかるように、８００℃および８５０℃付近での熱耐久試験後のＮＯｘ浄化効率については本参考形態の触媒と従来の触媒とにさほどの差異は見られないが、９００℃付近での熱耐久試験後のＮＯｘ浄化効率についていえば本参考形態のものは従来のものに比べて相当に向上している。これは、本参考形態の触媒が高温耐久後の浄化性能に優れることを示す。
図３は、８５０℃で２０時間の熱耐久試験を実施した後で床下触媒の形式で構成した本参考形態の触媒および従来の触媒を使用したときの、床下触媒入口温度とＮＯｘ浄化効率との関係を示し、四角形マークは本参考形態の触媒の特性を示し、丸マークは従来の触媒の特性を示す。図３からわかるように、床下触媒入口温度が５５０℃の場合を除き、本参考形態の触媒は従来のものに比べて熱耐久試験後のＮＯｘ浄化効率が向上しており、実車での通常の使用環境に対応する床下触媒入口温度が４００ないし４５０℃での浄化効率に優れている。
【００２１】
繰り返し云えば、図２及び図３に示した実験結果からわかるように、本参考考態の触媒によれば熱耐久後においても高い浄化性能が維持される。
以下、本発明の第１実施形態による排ガス浄化用触媒を説明する。
本実施形態の触媒は、そのＮＯｘ吸蔵・浄化能力を良好に維持すると共に熱耐久性を向上することを企図したものであり、参考形態のもの（図１）と基本構成が同一であるが、図４に示すように、触媒層（以下、第１触媒層という）２０の上層たとえば外面に第２触媒層３０を形成した点で参考形態のものと構成を異にする。
【００２２】
図４を参照すると、排ガス浄化用触媒は、コージライト担体１０と、担体１０の表面に担持され且つ貴金属、吸蔵剤および複合酸化物を含む第１触媒層２０と、第１触媒層２０の上層たとえば表面に形成された第２触媒層３０とからなる。担体１０、第１触媒層２０の構成は参考形態のものと同一であるので、説明を省略する。第２触媒層３０は、プラチナなどの貴金属とカリウムやバリウム等のＮＯｘ吸蔵剤との混合物からなるもので、複合酸化物を含まない点で第１触媒層２０と相違する。
【００２３】
上記構成の排ガス浄化用触媒は、参考形態の場合と同様の手順で第１触媒層２０を担持したコージライト担体１０を、貴金属及びＮＯｘ吸蔵剤を含むスラリー中に浸漬し、これを乾燥・焼成することにより製造される。
既述のように、電子供与性の強いＮＯｘ吸蔵剤によって貴金属の酸化性能が低下して触媒のＮＯｘ吸蔵・浄化性能の悪化原因になるが、本実施形態の触媒の触媒層は、複合酸化物を含む第１触媒層２０と、その外面に形成され且つ複合酸化物を含まない第２触媒層３０とから構成され、第２触媒層３０内のＮＯｘ吸蔵剤が第１触媒層２０側へ移動し易くなっているため、吸蔵剤が第１触媒層２０内に集まって第２触媒層３０内の吸蔵剤の量は少なくなる。この結果、第２触媒層３０の貴金属の酸化作用が第２触媒層３０内の吸蔵剤により弱化され難くなり、触媒層全体とくに第２触媒層３０での貴金属の酸化作用ひいては触媒の吸蔵・浄化能力が高レベルに維持される。また、第２触媒層３０内の吸蔵剤の量が少なくなるため、第２触媒層３０からの吸蔵剤の飛散が抑制され、触媒の吸蔵能力が維持される。その他の作用効果については参考形態のものと同様であるので、説明を省略する。
【００２４】
以下、本発明の第２実施形態による排ガス浄化用触媒を説明する。
本実施形態の触媒は、図４に示した第１実施形態のものと基本構成が同一であるが、図５に示すように、第２触媒層３０をコージライト担体１０と第１触媒層２０との間に形成した点で第１実施形態のものと異なる。
すなわち、図５に示すように、本実施形態の排ガス浄化用触媒は、コージライト担体１０と、担体１０の表面に担持され且つ貴金属とＮＯｘ吸蔵剤とを含む第２触媒層３０と、その表面に形成され且つ貴金属、吸蔵剤および複合酸化物を含む第１触媒層２０とからなる。担体１０、第１触媒層２０及び第２触媒層３０の構成は第１実施形態のものと同一であるので、説明を省略する。
【００２５】
上記構成の排ガス浄化用触媒は、第２触媒層３０を担持したコージライト担体１０を貴金属、ＮＯｘ吸蔵剤および複合酸化物を含むスラリー中に浸漬し、これを乾燥・焼成することにより製造される。
本実施形態の排ガス浄化用触媒では、第１触媒層２０とコージライト担体１０との間に形成した第２触媒層３０に添加された吸蔵剤が、第１触媒層２０に混入されている複合酸化物中のＳｉによって引き寄せられ、従って、排ガスと接触し易い第１触媒層２０側に吸蔵剤が集まる。このため、排ガス浄化用触媒の吸蔵能力を排ガス空燃比のリッチ化により効率良く回復することができ、リッチ化に伴う燃費悪化を最小にでき、また、第２触媒層３０では吸蔵剤による貴金属の酸化作用の低下を抑制できるので、排ガス浄化用触媒の吸蔵・浄化能力は高レベルに維持される。その他の点については参考形態及び第１実施形態の場合と同様である。
【００２６】
以下、本発明の第３実施形態による排ガス浄化用触媒を説明する。
本実施形態の触媒は、図１に示した参考形態のものと基本構成が同一であるが、触媒層の外面に三元触媒層を形成した点で異なる。
図６に示すように、排ガス浄化用触媒は、コージライト担体１０と、担体１０の表面に担持され且つ貴金属、吸蔵剤および複合酸化物を含む触媒層２０と、この触媒層の表面に形成され且つ主に三元触媒作用を奏する三元触媒層４０とからなる。本実施形態において、三元触媒層４０には酸性質材料が影響抑止材料として混入され、三元触媒層４０に達した吸蔵剤が三元触媒層に対して及ぼす悪影響が緩和される。すなわち、吸蔵剤が、三元触媒層４０中の貴金属のＣＯ、ＨＣ吸着作用を弱化したり貴金属表面を覆うという悪影響を影響抑止材料により緩和するようにしている。酸性質材料としては、アルカリ塩である吸蔵剤と反応して安定物質を生成するシリカ（ＳｉＯ２）、タングステン（Ｗ）、リン（Ｐ）が用いられる。その一方で、三元触媒層４０には吸蔵剤が一切添加されておらず、良好な三元性能を得るようにしている。
【００２７】
上記構成の排ガス浄化用触媒は、参考形態の場合と同様の手順で第１触媒層２０を担持したコージライト担体１０を、プラチナ（Ｐｔ）、パラジウム（Ｐｄ）、ロジウム（Ｒｈ）などの貴金属と酸性質材料とを含むスラリー中に浸漬し、これを乾燥・焼成することにより製造される。
上記構成の排ガス浄化用触媒の作用を説明する。
【００２８】
触媒層２０では吸蔵剤が複合酸化物中のＳｉのまわりに固定され、高温下における飛散やコージライト担体１０および三元触媒層４０への移動が防止される。
そして、この様な移動抑制作用にも関わらず吸蔵剤が三元触媒層４０に到達した場合には、吸蔵剤が三元触媒層４０中の酸性質材料と反応して安定物質たとえばリン酸カリウムに変換され、これにより、三元触媒層４０に対する吸蔵剤の影響が緩和される。本実施形態によれば、触媒層２０と三元触媒層４０とを共通の担体１０上に形成して単一の触媒として安価に構成できる。また、排ガス浄化用触媒は、触媒層２０のＮＯｘ吸蔵性能および三元触媒層４０の三元性能に優れ、リーン運転時のＮＯｘ浄化が確実になされると共にストイキ運転時やリッチ運転時に発生するＣＯ，ＨＣが三元触媒層４０により浄化される。その他の点は参考形態の場合と同様である。
【００２９】
以下、本発明の第４実施形態による排ガス浄化用触媒を説明する。
本実施形態の触媒は、図６に示した第３実施形態のものと基本構成が同一であるが、三元触媒層をコージライト担体と触媒層との間に形成した点で異なる。
すなわち、図７に示すように、本実施形態の排ガス浄化用触媒は、コージライト担体１０と、担体１０の表面に担持された三元触媒層４０と、この三元触媒層４０の表面に形成された触媒層２０とからなる。この排ガス浄化用触媒は、触媒層２０を担持したコージライト担体１０を、貴金属と影響抑止材料たとえば酸性質材料とを含むスラリー中に浸漬し、これを乾燥・焼成することにより製造される。
【００３０】
本実施形態の排ガス浄化用触媒によれば、触媒層２０によりＮＯｘ浄化作用が奏されると共に三元触媒層４０により主にストイキまたはリッチ運転時の排ガス浄化作用が奏される。そして、触媒層２０では吸蔵剤が複合酸化物中のＳｉのまわりに固定され、高温下における飛散やコージライト担体１０および三元触媒層４０への移動が防止され、また、吸蔵剤が三元触媒層４０に到達した場合には、吸蔵剤が三元触媒層４０中の酸性質材料と反応して安定物質に変換され、三元触媒層４０に対する吸蔵剤の悪影響が抑制される。その他の点は参考形態の場合と同様である。
【００３１】
本発明は、上記第１ないし第４実施形態のものに限定されず、種々に変形可能である。
例えば、上記実施形態では、ハニカム型コージライト担体１０を担体として用いたが、本発明は、コージライト以外の材料から成る担体を備えた排ガス浄化用触媒にも適用可能である。メタル担体を用いた場合には、担体への吸蔵剤の浸透はほとんど問題にはならないが、吸蔵剤の飛散を防止する効果が得られ、触媒の排ガス浄化性能の低下が防止される。また、ハニカム型コージライト担体を用いる場合、コージライト担体のセルは四角形状のものに限定されず、例えば三角形状や六角形状のものでも良い。
【００３２】
また、上記実施形態では、触媒層２０に混入される複合酸化物として珪酸ジルコニウムを用いたが、これに代えて、コバルト、ジルコニウム、鉄、マンガンからなる遷移金属の群から選択される少なくとも一つと珪素とからなる複合酸化物を使用可能である。
また、第１ないし第４実施形態において述べた第２触媒層、三元触媒層の２つを触媒層と組み合わせてなる排ガス浄化用触媒を構成可能である。
【００３３】
【発明の効果】
請求項１に係る発明によれば、吸蔵剤を添加した触媒層に、コバルト、ジルコニウム、鉄およびマンガンの少なくとも一つと珪素とからなる複合酸化物を混入したので、高温下においても安定な複合酸化物中の珪素が奏する吸蔵剤移動抑制機能により触媒層における吸蔵剤の移動が抑制され、吸蔵剤の飛散や担体成分との反応による消失および吸蔵剤の硫黄被毒が抑制される。従って、高温雰囲気中で使用した場合にも排ガス浄化用触媒の吸蔵性能が維持され、高温耐久後にも吸蔵、浄化性能の低下を来すおそれが少なくなる。
【００３４】
更に、吸蔵剤を添加してなる第２触媒層を触媒層の上層に形成したので、第２触媒層に添加された吸蔵剤が触媒層内の複合酸化物中の珪素によって引き寄せられ、第２触媒層ひいては全触媒層からの吸蔵剤の飛散および第２触媒層での貴金属の酸化作用低下を抑制して、排ガス浄化用触媒の吸蔵・浄化能力を高レベルに維持することができる。
【００３５】
請求項２の発明によれば、吸蔵剤を添加してなる第２触媒層を触媒層と担体との間に形成したので、排ガスと接触し易い触媒層上層側に吸蔵剤が集まるため排ガス浄化用触媒の吸蔵能力を排ガスのリッチ化により効率良く回復することができ、また、第２触媒層における貴金属の酸化作用低下を抑制することができ、吸蔵・浄化能力を高レベルに維持できる。
【００３６】
請求項３の発明によれば、触媒層の上層または触媒層と担体との間の一方あるいは双方に三元触媒層を設けたので、触媒層に混入された複合酸化物中の珪素の移動抑制機能により触媒層から三元触媒層への吸蔵剤の移動ひいては三元触媒層における貴金属の酸化作用低下を抑制して三元触媒層の浄化性能を維持できる。
請求項４の発明によれば、複合酸化物として珪酸ジルコニウムを用いるので、熱耐久性に優れた排ガス浄化用触媒を安価に提供することができる。
【図面の簡単な説明】
【図１】 本発明の参考形態による排ガス浄化用触媒の一つのシェルの四半部を示す部分拡大断面図である。
【図２】 珪酸ジルコニウムを触媒層に含む排ガス浄化用触媒およびゼオライトを含む従来の触媒のそれぞれの熱耐久後のＮＯｘ浄化効率を耐久温度の関数として示す図である。
【図３】 触媒層中に珪酸ジルコニウムを含む触媒の熱耐久後の床下入口温度−ＮＯｘ浄化効率特性を従来の触媒の特性と比較して示す図である。
【図４】 本発明の第１実施形態による触媒のシェルの四半部を示す断面図である。
【図５】 本発明の第２実施形態による触媒のシェルの四半部を示す断面図である。
【図６】 本発明の第３実施形態による触媒のシェルの四半部を示す断面図である。
【図７】 本発明の第４実施形態による触媒のシェルの四半部を示す断面図である。
【符号の説明】
１０ コージライト担体
２０ 触媒層
３０ 第２触媒層
４０ 三元触媒層 [0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification catalyst, and more particularly to an exhaust gas purification catalyst excellent in durability and exhaust gas purification performance.
[0002]
[Related background]
Lean burn engines such as lean burn engines and in-cylinder injection engines are often operated at a lean air-fuel ratio on the lean fuel side, but the exhaust gas purification action of the three-way catalyst is not fully demonstrated during lean operation. In general, a NOx storage catalyst in which a catalyst layer to which a storage agent is added is supported on a cordierite carrier is mounted. However, in the case of NOx occlusion catalysts, particularly catalysts added with alkali metals as occlusion agents, the occlusion agent is scattered at a high temperature or moved into the cordierite carrier, so that the amount of occlusion agent is reduced. The problem that NOx occlusion capacity falls arises.
[0003]
For this reason, the present applicant has proposed to suppress scattering of the occluding agent and transfer to the carrier by adding zeolite to the catalyst in Japanese Patent Application No. 11-370358 (Japanese Patent Laid-Open No. 2001-129402). ing. Since silicon (Si) contained in zeolite has acid properties and high affinity with alkali, it exerts an action of attracting an occlusion agent that shows alkalinity, and therefore suppresses movement of zeolite as proposed above. By using as an agent, scattering and movement of the storage agent can be suppressed. Furthermore, since Si is mixed as zeolite, it does not react with the occluding agent to form a stable substance, and the disappearance of the occluding agent and thus the decrease in the occluding ability of the catalyst can be suppressed, even after operation at high temperatures. The catalyst maintains high NOx storage performance.
[0004]
[Problems to be solved by the invention]
As described above, the NOx occlusion catalyst to which zeolite is added can maintain high NOx occlusion performance even after operation at a high temperature. However, even when this type of catalyst is operated at a severe high temperature, the NOx occlusion performance thereafter is reduced. Accordingly, there is a demand for providing a catalyst with a reduced performance degradation after high-temperature durability.
[0005]
Therefore, as a result of further research in order to respond to such a request, it is an obstacle that the zeolite itself is a relatively low heat-resistant substance in order to suppress the performance degradation of the NOx storage catalyst after high-temperature durability. Turned out to be. That is, the zeolite is a predominantly composite oxide of SiO 2 and Al 2 O 3, easily collapse the bond between SiO 2 and Al 2 O 3 at a high temperature, and if the two coupling collapses SiO 2 or Si is occluded It becomes easy to react with the agent, the reaction with SiO 2 or Si proceeds, the occlusion agent acting on the NOx occlusion reaction disappears correspondingly, and the occlusion performance of the catalyst is lowered.
[0006]
Therefore, the present invention provides an exhaust gas purification catalyst that is excellent in high temperature durability, and in particular, can reduce the deterioration degree of exhaust gas purification performance due to the disappearance of the occlusion agent that acts on the NOx occlusion reaction under severe high temperatures. Objective.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 includes a support and a catalyst layer, and at least one selected from the group consisting of alkali metals and alkaline earth metals is added to the catalyst layer as an occlusion agent. In the catalyst layer, a composite oxide comprising at least one metal selected from the group of transition metals consisting of cobalt (Co), zirconium (Zr), iron (Fe), and manganese (Mn) and silicon (Si) is used as the catalyst layer. It is characterized by mixing.
[0008]
In the present invention, silicate (Si in the composite oxide) has an action of attracting the occluding agent, and does not cause a chemical reaction that generates a stable substance with the occluding agent. For this reason, the occlusion agent is held in the vicinity of Si without losing its original function, that is, the occlusion function, and therefore the movement of the occlusion agent in the catalyst layer is suppressed. As a result, the occlusion agent disappears due to the scattering of the occlusion agent or the chemical reaction between the occlusion agent moved into the carrier and the carrier composition, and the sulfur poisoning of the occlusion agent (due to the reaction between the sulfur content in the fuel or exhaust gas and the occlusion agent (Sulfate formation) is suppressed, and the occlusion performance of the catalyst is maintained.
[0009]
Moreover, the transition metals Co, Zr, Fe, and Mn have a high melting point, and the composite oxides of these transition metals and Si exhibit high thermal stability. Accordingly, the effect of suppressing the movement of the occluding agent by the Si in the composite oxide and the occluding function of the occluding agent are maintained even at high temperatures. That is, a catalyst in which a composite oxide composed of a transition metal and silicon is mixed in a catalyst layer is excellent in heat durability performance, and the occlusion performance is maintained even after high temperature durability.
[0010]
Furthermore, in the invention described in claim 1 , the second catalyst layer formed by adding at least one selected from the group consisting of alkali metals and alkaline earth metals as an occlusion agent is formed on the upper layer of the catalyst layer. It is characterized by.
In the first aspect of the present invention, the second catalyst layer does not contain a complex oxide composed of a transition metal and silicon, and the storage agent added to the second catalyst layer is mixed into the catalyst layer following the second catalyst layer. It is attracted by the complex oxide Si. Therefore, since the amount of the storage agent in the second catalyst layer is reduced, scattering of the storage agent from the second catalyst layer and thus from all the catalyst layers is suppressed, and a decrease in the storage capacity of the catalyst is prevented. Further, the occlusion agent made of alkali metal or alkaline earth metal has a strong electron donating property and can cause a reduction in the oxidizing action of the noble metal. In the invention of claim 2, the amount of the occlusion agent in the second catalyst layer. Therefore, the decrease in the oxidation effect of the noble metal in the second catalyst layer is suppressed. That is, according to the catalyst provided with the second catalyst layer in the upper layer of the catalyst layer, the occlusion / purification capability is maintained at a high level.
[0011]
In the invention according to claim 2 , the second catalyst layer is formed by adding at least one selected from the group consisting of alkali metals and alkaline earth metals as a storage agent between the catalyst layer and the support. It is characterized by.
In the invention of claim 2 , the catalyst layer is formed on the catalyst surface side, the second catalyst layer is formed between the catalyst layer and the carrier, and the storage agent added to the second catalyst layer is included in the catalyst layer. It is attracted by Si in the complex oxide. Therefore, the occlusion agent collects on the upper layer side of the catalyst layer that easily comes into contact with the exhaust gas. Therefore, the occlusion capacity can be efficiently recovered by enriching the exhaust gas air-fuel ratio. Since the recovery efficiency is high in this manner, fuel consumption deterioration due to enrichment can be minimized, and the storage agent in the second catalyst layer is attracted to the catalyst layer that follows the second catalyst layer, so that oxidation of the noble metal in the second catalyst layer is performed. Decrease in action can be suppressed. That is, the storage / purification capacity of the catalyst is maintained at a high level.
[0012]
The invention described in claim 3 is characterized in that a three-way catalyst layer is provided on the upper layer of the catalyst layer and at least one of the catalyst layer and the carrier.
In the invention of claim 3 , since Si in the composite oxide has a storage agent holding action, the movement of the storage agent to the three-way catalyst layer is suppressed, and the decrease in the oxidation action of the noble metal by the storage agent is suppressed. The purification performance of the original catalyst layer and thus the catalyst is maintained .
[0013]
The invention of claim 4 is characterized in that zirconium silicate (ZrSiO4) is used as the composite oxide.
Zirconium silicate is an industrially easily available material. Therefore, by mixing the composite oxide composed of zirconium silicate into the catalyst layer to which the occluding agent is added, it is expected to prevent the occluding agent from moving and scattering. The objective can be achieved at low cost.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
First, an exhaust gas purifying catalyst according to a reference embodiment of the present invention will be described.
The exhaust gas purifying catalyst of the present embodiment is configured as a NOx catalyst having a honeycomb (monolith) type cordierite carrier composed of a large number of cells. FIG. 1 shows a part of one cell of the cordierite carrier, and the cell of the cordierite carrier 10 is formed in a square shape, for example. A catalyst layer 20 is supported on the surface of the cordierite carrier 10. The catalyst layer 20 is added with a noble metal such as platinum (Pt) and palladium (Pd) and a NOx storage agent such as potassium (K) and barium (Ba), and also cobalt (Co) and zirconium ( A composite oxide composed of at least one metal selected from the group of transition metals composed of Zr), iron (Fe), and manganese (Mn) and silicon (Si) is mixed therein. In this reference embodiment , zirconium silicate (ZrSiO4) is used as the composite oxide.
[0015]
Preferably, each supported amount of platinum and palladium is set to a value of 0.1 to 10 g per liter of support, and each supported amount of potassium and barium is set to a value of 0.1 to 50 g per liter of support. In addition, the amount of zirconium silicate supported is set to a value of 0.1 to 50 g per liter of the carrier.
The cordierite carrier 10 is, for example, a mixture of an alumina source powder, a silica source powder, and a magnesia source powder mixed so that the proportions of alumina, silica, and magnesia are cordierite composition. The portion is formed into a honeycomb shape, and this honeycomb formed body is fired.
[0016]
The catalyst layer 20 is supported on the surface of the cordierite carrier 10 as follows, for example.
First, a slurry containing a powder mainly composed of a noble metal such as platinum, an alkali metal such as potassium, an alkaline earth metal such as barium, and zirconium silicate as a composite oxide is prepared. Next, the cordierite carrier 10 is immersed in the slurry, which is dried and fired.
[0017]
As described above, a NOx catalyst obtained by coating the cordierite carrier 10 with the catalyst layer 20 is obtained. As conventionally known, this NOx catalyst is accommodated in a case through a buffer material, for example, and is disposed in an exhaust pipe of a lean combustion internal combustion engine.
According to this NOx catalyst, NOx in the exhaust gas is occluded in the form of nitrate under the action of the catalyst species dispersed in the catalyst layer 20 during engine operation at a lean air-fuel ratio. Further, during engine operation at a rich air-fuel ratio, nitrate is decomposed, and the stored NOx is reduced to nitrogen and released from the NOx catalyst into the atmosphere.
[0018]
When the NOx catalyst is exposed to a high temperature for a long time, generally, the occlusion agent added to the catalyst layer, for example, potassium moves into the cordierite carrier and reacts with silicon in the carrier to form a compound. However, in the NOx catalyst of the present embodiment , the movement of the storage agent such as potassium in the catalyst layer 20 is held near the silicon (Si) contained in the zirconium silicate. The movement to the cordierite carrier 10 is prevented, and the generation of cracks is prevented.
[0019]
In addition, according to the catalyst in which the zeolite that suppresses the movement of the occluding agent is mixed in the catalyst layer, the bonding between the constituent components SiO 2 and Al 2 O 3 is broken at a severe high temperature, and the occluding agent disappears. Although the NOx purification efficiency later decreases, the composite oxide of zirconium silicate and silicon mixed in the catalyst layer of the present embodiment has high thermal stability and suppresses the movement of the occluding agent by Si in the composite oxide. Is maintained even at a high temperature exceeding 850 ° C., for example, and is excellent in NOx purification efficiency after high-temperature durability.
[0020]
In order to confirm the above-mentioned actions and effects, the inventor of each of the NOx catalyst of this embodiment in which a composite oxide of zirconium silicate and silicon is mixed in the catalyst layer and the conventional NOx catalyst in which zeolite is mixed are endured by heat. The NOx purification efficiency after the test was measured, and the measurement results are shown in FIGS.
FIG. 2 shows the relationship between the endurance temperature (catalyst temperature in the thermal endurance test) and the NOx purification efficiency after the thermal endurance test, that is, the endurance temperature-NOx purification efficiency characteristics of the catalyst. The evaluation temperature is 500 ° C. In FIG. 2, square marks indicate the characteristics of the catalyst of the present embodiment , triangle marks indicate the characteristics of the conventional catalyst, and broken lines indicate the characteristics of the new (before deterioration) catalyst. As can be seen from FIG. 2, the NOx purification efficiency after the thermal endurance test near 800 ° C. and 850 ° C. is not so different between the catalyst of this embodiment and the conventional catalyst. Regarding the NOx purification efficiency after the thermal endurance test, the present embodiment is considerably improved compared to the conventional one. This indicates that the catalyst of the present embodiment is excellent in purification performance after high temperature durability.
FIG. 3 shows the relationship between the underfloor catalyst inlet temperature and the NOx purification efficiency when the catalyst of the present embodiment and the conventional catalyst configured in the form of an underfloor catalyst after performing a thermal durability test at 850 ° C. for 20 hours. The square marks indicate the characteristics of the catalyst of the present embodiment , and the circle marks indicate the characteristics of the conventional catalyst. As can be seen from FIG. 3, except for the case where the underfloor catalyst inlet temperature is 550 ° C., the catalyst of this reference embodiment has improved NOx purification efficiency after the thermal endurance test compared to the conventional one, and is normal in an actual vehicle. It has excellent purification efficiency when the underfloor catalyst inlet temperature corresponding to the use environment is 400 to 450 ° C.
[0021]
In other words, as can be seen from the experimental results shown in FIG. 2 and FIG. 3, the catalyst of this reference state maintains high purification performance even after thermal endurance.
Hereinafter, the exhaust gas purifying catalyst according to the first embodiment of the present invention will be described.
The catalyst of the present embodiment is intended to maintain its NOx occlusion / purification ability well and improve the heat durability, and has the same basic configuration as that of the reference embodiment (FIG. 1). As shown in FIG. 4, the configuration is different from that of the reference embodiment in that a second catalyst layer 30 is formed on an upper layer, for example, the outer surface of a catalyst layer (hereinafter referred to as a first catalyst layer) 20.
[0022]
Referring to FIG. 4, the exhaust gas purifying catalyst includes a cordierite carrier 10, a first catalyst layer 20 supported on the surface of the carrier 10 and containing a noble metal, a storage agent, and a composite oxide, and an upper layer of the first catalyst layer 20. For example, it consists of the second catalyst layer 30 formed on the surface. Since the structure of the support | carrier 10 and the 1st catalyst layer 20 is the same as that of a reference form , description is abbreviate | omitted. The second catalyst layer 30 is made of a mixture of a noble metal such as platinum and a NOx storage agent such as potassium or barium, and is different from the first catalyst layer 20 in that it does not contain a complex oxide.
[0023]
In the exhaust gas purifying catalyst having the above-described configuration, the cordierite carrier 10 carrying the first catalyst layer 20 is immersed in a slurry containing a noble metal and a NOx storage agent in the same procedure as in the reference embodiment , and this is dried and calcined. It is manufactured by doing.
As described above, the NOx occlusion agent having a strong electron donating property lowers the oxidation performance of the noble metal and causes deterioration of the NOx occlusion / purification performance of the catalyst. However, the catalyst layer of the catalyst of this embodiment is a composite oxide. And a second catalyst layer 30 that is formed on the outer surface and does not contain a complex oxide, and the NOx storage agent in the second catalyst layer 30 moves to the first catalyst layer 20 side. Therefore, the occlusion agent gathers in the first catalyst layer 20 and the amount of the occlusion agent in the second catalyst layer 30 decreases. As a result, the oxidation action of the noble metal in the second catalyst layer 30 is not easily weakened by the occlusion agent in the second catalyst layer 30, and the oxidation action of the noble metal in the entire catalyst layer, particularly the second catalyst layer 30, and thus the occlusion / purification of the catalyst. Ability is maintained at a high level. Further, since the amount of the storage agent in the second catalyst layer 30 is reduced, the storage of the storage agent from the second catalyst layer 30 is suppressed, and the storage capacity of the catalyst is maintained. Other operational effects are the same as those of the reference embodiment , and thus description thereof is omitted.
[0024]
Hereinafter, an exhaust gas purifying catalyst according to a second embodiment of the present invention will be described.
The catalyst of the present embodiment has the same basic configuration as that of the first embodiment shown in FIG. 4, but as shown in FIG. 5, the second catalyst layer 30 is composed of the cordierite carrier 10 and the first catalyst layer 20. It differs from the thing of 1st Embodiment by the point formed between.
That is, as shown in FIG. 5, the exhaust gas purifying catalyst of this embodiment includes a cordierite carrier 10, a second catalyst layer 30 supported on the surface of the carrier 10 and containing a noble metal and a NOx storage agent, and its surface. And a first catalyst layer 20 containing a noble metal, a storage agent and a composite oxide. Since the structure of the support | carrier 10, the 1st catalyst layer 20, and the 2nd catalyst layer 30 is the same as the thing of 1st Embodiment , description is abbreviate | omitted.
[0025]
The exhaust gas purifying catalyst having the above-described configuration is manufactured by immersing the cordierite carrier 10 supporting the second catalyst layer 30 in a slurry containing a noble metal, a NOx storage agent and a composite oxide, and drying and firing the slurry. .
In the exhaust gas purifying catalyst according to the present embodiment, the occlusion agent added to the second catalyst layer 30 formed between the first catalyst layer 20 and the cordierite carrier 10 is mixed in the first catalyst layer 20. Therefore, the occlusion agent collects on the first catalyst layer 20 side that is attracted by Si in the oxide and is easily in contact with the exhaust gas. For this reason, the storage capacity of the exhaust gas purifying catalyst can be efficiently recovered by enriching the exhaust gas air-fuel ratio, the deterioration of fuel consumption accompanying the enrichment can be minimized, and in the second catalyst layer 30, noble metal by the storage agent can be reduced. Since the reduction in oxidation action can be suppressed, the storage / purification capacity of the exhaust gas purifying catalyst is maintained at a high level. About another point, it is the same as that of the case of a reference form and 1st Embodiment .
[0026]
Hereinafter, an exhaust gas purifying catalyst according to a third embodiment of the present invention will be described.
The catalyst of the present embodiment has the same basic configuration as that of the reference embodiment shown in FIG. 1, but differs in that a three-way catalyst layer is formed on the outer surface of the catalyst layer.
As shown in FIG. 6, the exhaust gas purifying catalyst is formed on the surface of the cordierite carrier 10, the catalyst layer 20 supported on the surface of the carrier 10 and containing a noble metal, an occlusion agent, and a composite oxide. The three-way catalyst layer 40 mainly exhibits a three-way catalytic action. In the present embodiment, an acid property material is mixed in the three-way catalyst layer 40 as an influence-inhibiting material, and the adverse effect of the storage agent reaching the three-way catalyst layer 40 on the three-way catalyst layer is mitigated. That is, the occlusion agent attenuates the adverse effect of weakening the CO and HC adsorption action of the noble metal in the three-way catalyst layer 40 or covering the surface of the noble metal by the influence suppressing material. As an acid property material, silica (SiO 2 ), tungsten (W), or phosphorus (P) that reacts with an occlusion agent that is an alkali salt to generate a stable substance is used. On the other hand, no occlusion agent is added to the three-way catalyst layer 40, so that good three-way performance is obtained.
[0027]
In the exhaust gas purifying catalyst having the above-described configuration, the cordierite carrier 10 supporting the first catalyst layer 20 in the same procedure as in the reference embodiment is combined with a noble metal such as platinum (Pt), palladium (Pd), rhodium (Rh). It is manufactured by immersing it in a slurry containing an acid property material, and drying and firing it.
The operation of the exhaust gas purifying catalyst having the above configuration will be described.
[0028]
In the catalyst layer 20, the occlusion agent is fixed around the Si in the composite oxide, and scattering at a high temperature and movement to the cordierite carrier 10 and the three-way catalyst layer 40 are prevented.
When the occlusion agent reaches the three-way catalyst layer 40 in spite of such a movement suppressing action, the occlusion agent reacts with the acid property material in the three-way catalyst layer 40 to react with a stable substance such as potassium phosphate. Thus, the influence of the storage agent on the three-way catalyst layer 40 is mitigated. According to the present embodiment, the catalyst layer 20 and the three-way catalyst layer 40 can be formed on the common carrier 10 and configured as a single catalyst at low cost. Further, the exhaust gas purifying catalyst is excellent in the NOx occlusion performance of the catalyst layer 20 and the three-way performance of the three-way catalyst layer 40, and the NOx purification during the lean operation is ensured and the CO generated during the stoichiometric operation and the rich operation is achieved. , HC are purified by the three-way catalyst layer 40. Other points are the same as in the case of the reference embodiment .
[0029]
Hereinafter, an exhaust gas purifying catalyst according to a fourth embodiment of the present invention will be described.
The catalyst of this embodiment has the same basic configuration as that of the third embodiment shown in FIG. 6, but differs in that a three-way catalyst layer is formed between the cordierite carrier and the catalyst layer.
That is, as shown in FIG. 7, the exhaust gas purifying catalyst of the present embodiment is formed on the cordierite carrier 10, the three-way catalyst layer 40 supported on the surface of the carrier 10, and the surface of the three-way catalyst layer 40. Catalyst layer 20 formed. The exhaust gas-purifying catalyst is produced by immersing the cordierite carrier 10 carrying the catalyst layer 20 in a slurry containing a noble metal and an influence-inhibiting material such as an acid property material, and drying and firing the slurry.
[0030]
According to the exhaust gas purifying catalyst of the present embodiment, the NOx purification action is exhibited by the catalyst layer 20, and the exhaust gas purification action at the time of stoichiometric or rich operation is exhibited mainly by the three-way catalyst layer 40. In the catalyst layer 20, the occlusion agent is fixed around the Si in the composite oxide, and scattering at high temperatures and movement to the cordierite carrier 10 and the three-way catalyst layer 40 are prevented, and the occlusion agent is ternary. When the catalyst layer 40 is reached, the storage agent reacts with the acidic material in the three-way catalyst layer 40 and is converted into a stable substance, and the adverse effect of the storage agent on the three-way catalyst layer 40 is suppressed. Other points are the same as in the case of the reference embodiment .
[0031]
The present invention is not limited to the first to fourth embodiments , and can be variously modified.
For example, in the above-described embodiment, the honeycomb type cordierite carrier 10 is used as a carrier, but the present invention is also applicable to an exhaust gas purification catalyst provided with a carrier made of a material other than cordierite. When a metal carrier is used, penetration of the occluding agent into the carrier poses no problem, but an effect of preventing the occluding agent from scattering is obtained, and a reduction in the exhaust gas purification performance of the catalyst is prevented. Further, when the honeycomb type cordierite carrier is used, the cordierite carrier cell is not limited to a rectangular shape, and may be, for example, a triangular shape or a hexagonal shape.
[0032]
Moreover, in the said embodiment, although the zirconium silicate was used as a complex oxide mixed in the catalyst layer 20, instead of this, at least one selected from the group of transition metals consisting of cobalt, zirconium, iron, and manganese; A composite oxide made of silicon can be used .
Further, it is possible to configure an exhaust gas purification catalyst in which two of the second catalyst layer and the three-way catalyst layer described in the first to fourth embodiments are combined with a catalyst layer.
[0033]
【The invention's effect】
According to the invention of claim 1, since the composite oxide composed of at least one of cobalt, zirconium, iron and manganese and silicon is mixed in the catalyst layer to which the storage agent is added, the composite oxidation stable even at high temperatures. The movement of the storage agent in the catalyst layer is suppressed by the function of suppressing the storage agent movement produced by silicon in the material, and the disappearance of the storage agent due to scattering and reaction with the carrier component and the sulfur poisoning of the storage agent are suppressed. Therefore, even when used in a high temperature atmosphere, the occlusion performance of the exhaust gas purifying catalyst is maintained, and the possibility of reducing the occlusion and purification performance after high temperature durability is reduced.
[0034]
Furthermore, since the second catalyst layer to which the storage agent is added is formed in the upper layer of the catalyst layer , the storage agent added to the second catalyst layer is attracted by silicon in the composite oxide in the catalyst layer, The occlusion / purification ability of the exhaust gas purifying catalyst can be maintained at a high level by suppressing the scattering of the occluding agent from the catalyst layer and thus the entire catalyst layer and the reduction of the oxidizing action of the noble metal in the second catalyst layer.
[0035]
According to the invention of claim 2 , since the second catalyst layer to which the storage agent is added is formed between the catalyst layer and the carrier, the storage agent collects on the upper layer side of the catalyst layer which is easily in contact with the exhaust gas. The occlusion capacity of the catalyst for use can be efficiently recovered by enriching the exhaust gas, and the decrease in the oxidizing action of the noble metal in the second catalyst layer can be suppressed, and the occlusion / purification capacity can be maintained at a high level.
[0036]
According to the invention of claim 3 , since the three-way catalyst layer is provided on one or both of the upper layer of the catalyst layer or between the catalyst layer and the carrier, the movement of silicon in the composite oxide mixed in the catalyst layer is suppressed. The function can suppress the movement of the storage agent from the catalyst layer to the three-way catalyst layer, and hence the reduction in the oxidation effect of the noble metal in the three-way catalyst layer, and maintain the purification performance of the three-way catalyst layer .
According to the invention of claim 4 , since zirconium silicate is used as the composite oxide, an exhaust gas purifying catalyst having excellent thermal durability can be provided at low cost.
[Brief description of the drawings]
FIG. 1 is a partially enlarged sectional view showing a quarter portion of one shell of an exhaust gas purifying catalyst according to a reference embodiment of the present invention.
FIG. 2 is a graph showing NOx purification efficiency after thermal endurance as a function of endurance temperature of an exhaust gas purification catalyst containing zirconium silicate in a catalyst layer and a conventional catalyst containing zeolite.
FIG. 3 is a diagram showing the underfloor inlet temperature-NOx purification efficiency characteristic after thermal endurance of a catalyst containing zirconium silicate in a catalyst layer in comparison with the characteristic of a conventional catalyst.
FIG. 4 is a cross-sectional view showing a quarter portion of the shell of the catalyst according to the first embodiment of the present invention.
FIG. 5 is a cross-sectional view showing a quarter part of a shell of a catalyst according to a second embodiment of the present invention.
FIG. 6 is a cross-sectional view showing a quarter part of a shell of a catalyst according to a third embodiment of the present invention.
FIG. 7 is a cross-sectional view showing a quarter portion of a shell of a catalyst according to a fourth embodiment of the present invention .
[Explanation of symbols]
10 Cordierite carrier 20 Catalyst layer 30 Second catalyst layer 40 Three-way catalyst layer

Claims (4)

担体と触媒層とを含み、前記触媒層にアルカリ金属及びアルカリ土類金属からなる群から選択される少なくとも一つを吸蔵剤として添加してなる排ガス浄化用触媒において、
コバルト（Ｃｏ）、ジルコニウム（Ｚｒ）、鉄（Ｆｅ）、マンガン（Ｍｎ）からなる遷移金属の群から選択される少なくとも一つの金属と珪素（Ｓｉ）とからなる複合酸化物を上記触媒層に混入するとともに、上記触媒層の上層に、アルカリ金属及びアルカリ土類金属からなる群から選択される少なくとも一つを吸蔵剤として添加してなる第２触媒層を形成したことを特徴とする排ガス浄化用触媒。In an exhaust gas purifying catalyst comprising a support and a catalyst layer, wherein at least one selected from the group consisting of alkali metals and alkaline earth metals is added as a storage agent to the catalyst layer,
A composite oxide composed of at least one metal selected from the group of transition metals composed of cobalt (Co), zirconium (Zr), iron (Fe), and manganese (Mn) and silicon (Si) is mixed in the catalyst layer. And a second catalyst layer formed by adding at least one selected from the group consisting of alkali metals and alkaline earth metals as an occlusion agent to the upper layer of the catalyst layer . catalyst. 担体と触媒層とを含み、前記触媒層にアルカリ金属及びアルカリ土類金属からなる群から選択される少なくとも一つを吸蔵剤として添加してなる排ガス浄化用触媒において、
コバルト（Ｃｏ）、ジルコニウム（Ｚｒ）、鉄（Ｆｅ）、マンガン（Ｍｎ）からなる遷移金属の群から選択される少なくとも一つの金属と珪素（Ｓｉ）とからなる複合酸化物を上記触媒層に混入するとともに、上記触媒層と担体との間に、アルカリ金属及びアルカリ土類金属からなる群から選択される少なくとも一つを吸蔵剤として添加してなる第２触媒層を形成したことを特徴とする排ガス浄化用触媒。 In an exhaust gas purifying catalyst comprising a support and a catalyst layer, wherein at least one selected from the group consisting of alkali metals and alkaline earth metals is added as a storage agent to the catalyst layer,
A composite oxide composed of at least one metal selected from the group of transition metals composed of cobalt (Co), zirconium (Zr), iron (Fe), and manganese (Mn) and silicon (Si) is mixed in the catalyst layer. And a second catalyst layer formed by adding at least one selected from the group consisting of an alkali metal and an alkaline earth metal as a storage agent between the catalyst layer and the carrier . that the exhaust gas purifying catalyst. 担体と触媒層とを含み、前記触媒層にアルカリ金属及びアルカリ土類金属からなる群から選択される少なくとも一つを吸蔵剤として添加してなる排ガス浄化用触媒において、
コバルト（Ｃｏ）、ジルコニウム（Ｚｒ）、鉄（Ｆｅ）、マンガン（Ｍｎ）からなる遷移金属の群から選択される少なくとも一つの金属と珪素（Ｓｉ）とからなる複合酸化物を上記触媒層に混入するとともに、上記触媒層の上層および上記触媒層と上記担体との間の少なくとも一方に三元触媒層を設けたことを特徴とする排ガス浄化用触媒。 In an exhaust gas purifying catalyst comprising a support and a catalyst layer, wherein at least one selected from the group consisting of alkali metals and alkaline earth metals is added as a storage agent to the catalyst layer,
A composite oxide composed of at least one metal selected from the group of transition metals composed of cobalt (Co), zirconium (Zr), iron (Fe), and manganese (Mn) and silicon (Si) is mixed in the catalyst layer. to together, the catalyst for exhaust gas purification you characterized by providing on at least one three-way catalyst layer between the upper layer and the catalyst layer and the carrier of the catalyst layer. 上記複合酸化物として珪酸ジルコニウム（ＺｒＳｉＯ４）を用いたことを特徴とする請求項１ないし３のいずれかに記載の排ガス浄化用触媒。 The exhaust gas purifying catalyst according to any one of claims 1 to 3, wherein zirconium silicate (ZrSiO4) is used as the composite oxide .
JP2001174469A 2001-06-08 2001-06-08 Exhaust gas purification catalyst Expired - Lifetime JP4645786B2 (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
JP2001174469A JP4645786B2 (en) 2001-06-08 2001-06-08 Exhaust gas purification catalyst
KR10-2002-0028841A KR100464715B1 (en) 2001-06-08 2002-05-24 Exhaust gas emission purifying catalyst
EP20020011690 EP1264629B1 (en) 2001-06-08 2002-06-03 Exhaust gas emission purifying catalyst
DE60201707T DE60201707T2 (en) 2001-06-08 2002-06-03 Catalyst for the purification of exhaust gases
US10/163,494 US6770590B2 (en) 2001-06-08 2002-06-07 Exhaust gas emission purifying catalyst

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2001174469A JP4645786B2 (en) 2001-06-08 2001-06-08 Exhaust gas purification catalyst

Publications (2)

Publication Number Publication Date
JP2002361094A JP2002361094A (en) 2002-12-17
JP4645786B2 true JP4645786B2 (en) 2011-03-09

Family

ID=19015749

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2001174469A Expired - Lifetime JP4645786B2 (en) 2001-06-08 2001-06-08 Exhaust gas purification catalyst

Country Status (5)

Country Link
US (1) US6770590B2 (en)
EP (1) EP1264629B1 (en)
JP (1) JP4645786B2 (en)
KR (1) KR100464715B1 (en)
DE (1) DE60201707T2 (en)

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6797663B2 (en) * 2001-02-26 2004-09-28 Mitsubishi Jidosha Kogyo Kabushiki Kaisha Catalyst for exhaust gas purification
JP4246075B2 (en) * 2003-03-07 2009-04-02 株式会社デンソー Method for producing ceramic catalyst body
JP4913727B2 (en) * 2005-03-18 2012-04-11 株式会社日本触媒 Oxygen removal catalyst and oxygen removal method using the catalyst
JP2006348767A (en) * 2005-06-13 2006-12-28 Mitsubishi Motors Corp Exhaust emission control device for internal combustion engine
US7749472B2 (en) * 2006-08-14 2010-07-06 Basf Corporation Phosgard, a new way to improve poison resistance in three-way catalyst applications
WO2008090991A1 (en) 2007-01-26 2008-07-31 Cataler Corporation Exhaust gas purifying catalyst
KR100892528B1 (en) 2007-12-12 2009-04-10 현대자동차주식회사 Composition of nox storage-reduction catalyst containg potassium and manganese
US8207084B2 (en) * 2009-06-23 2012-06-26 Ford Global Technologies, Llc Urea-resistant catalytic units and methods of using the same
GB2484911B (en) * 2010-10-22 2013-04-03 Johnson Matthey Plc NOx absorber catalyst comprising caesium silicate and at least one platinum group metal
CN105683518B (en) * 2013-09-16 2019-10-18 庄信万丰股份有限公司 With modified lean combustion NOxThe exhaust system and method for trap
GB201401115D0 (en) 2014-01-23 2014-03-12 Johnson Matthey Plc Diesel oxidation catalyst and exhaust system

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05177144A (en) * 1990-08-27 1993-07-20 Nippon Shokubai Co Ltd Strengthened catalyst for exhaust gas treatment
JP2001038211A (en) * 1999-07-30 2001-02-13 Toyota Central Res & Dev Lab Inc Catalyst and method for cleaning exhaust gas
JP2001046835A (en) * 1999-08-06 2001-02-20 Nissan Motor Co Ltd NOx ABSORBING AND CLEANING MATERIAL AND EXHAUST GAS CLEANING CATALYST USING THE SAME
JP2001129402A (en) * 1999-08-20 2001-05-15 Mitsubishi Motors Corp Catalyst for purifying exhaust gas
JP2001149757A (en) * 1999-11-29 2001-06-05 Cataler Corp Exhaust gas purifying catalyst

Family Cites Families (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4171287A (en) * 1977-09-23 1979-10-16 Engelhard Minerals & Chemicals Corporation Catalyst compositions and the method of manufacturing them
JP2897367B2 (en) * 1990-01-12 1999-05-31 日本特殊陶業株式会社 Poisoning prevention body, catalyst with poisoning prevention layer, and exhaust gas purification device
JP3098083B2 (en) * 1991-12-26 2000-10-10 マツダ株式会社 Exhaust gas purification catalyst
EP0613714B1 (en) * 1993-01-11 2001-07-04 Toyota Jidosha Kabushiki Kaisha Process for purifying exhaust gases
JP3375358B2 (en) * 1993-01-29 2003-02-10 マツダ株式会社 Exhaust gas purification catalyst
JP4098835B2 (en) * 1993-12-07 2008-06-11 トヨタ自動車株式会社 Exhaust gas purification catalyst
JP3363564B2 (en) * 1994-02-04 2003-01-08 トヨタ自動車株式会社 Exhaust gas purification catalyst
JP3511314B2 (en) * 1994-07-12 2004-03-29 株式会社キャタラー Exhaust gas purification catalyst and exhaust gas purification method
JP3799651B2 (en) * 1995-04-28 2006-07-19 マツダ株式会社 Exhaust gas purification catalyst
JP3839860B2 (en) 1995-09-22 2006-11-01 株式会社豊田中央研究所 Exhaust gas purification catalyst and exhaust gas purification method
US6426316B2 (en) * 1996-08-13 2002-07-30 Toyota Jidosha Kabushiki Kaisha Exhaust emission control catalyst for diesel engines
JP3956437B2 (en) * 1996-09-26 2007-08-08 マツダ株式会社 Exhaust gas purification catalyst
US6348430B1 (en) * 1997-06-20 2002-02-19 Degussa Ag Exhaust gas treatment catalyst for internal combustion engines with two catalytically active layers on a carrier structure
KR100446599B1 (en) * 1997-10-30 2004-10-14 삼성전기주식회사 Catalyst for purifying exhaust gas of automobiles
US6022825A (en) * 1998-01-08 2000-02-08 Johnson Matthey Public Limited Company Thermally durable low H2 S three-way catalysts
KR100326747B1 (en) * 1998-03-09 2002-03-13 하나와 요시카즈 Device for Purifying Oxygen Rich Exhaust Gas
JP2000024499A (en) * 1998-07-07 2000-01-25 Toyota Motor Corp Catalyst for purification of exhaust gas and its production
US6479428B1 (en) * 1998-07-27 2002-11-12 Battelle Memorial Institute Long life hydrocarbon conversion catalyst and method of making
JP2000176298A (en) * 1998-12-11 2000-06-27 Mazda Motor Corp Exhaust gas purification catalyst and its production
JP3952617B2 (en) * 1998-12-11 2007-08-01 株式会社日立製作所 Exhaust gas purification device, exhaust gas purification method and exhaust gas purification catalyst for internal combustion engine
JP3835659B2 (en) 1999-03-30 2006-10-18 トヨタ自動車株式会社 Exhaust gas purification catalyst
DE60042991D1 (en) * 1999-07-09 2009-11-05 Nissan Motor Exhaust gas purifying catalyst and process for its production
EP1078678B8 (en) * 1999-08-20 2010-02-17 Mitsubishi Jidosha Kogyo Kabushiki Kaisha Exhaust gas purifying catalyst
US6534438B1 (en) * 2000-07-26 2003-03-18 Bp Chemicals Limited Catalyst composition

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05177144A (en) * 1990-08-27 1993-07-20 Nippon Shokubai Co Ltd Strengthened catalyst for exhaust gas treatment
JP2001038211A (en) * 1999-07-30 2001-02-13 Toyota Central Res & Dev Lab Inc Catalyst and method for cleaning exhaust gas
JP2001046835A (en) * 1999-08-06 2001-02-20 Nissan Motor Co Ltd NOx ABSORBING AND CLEANING MATERIAL AND EXHAUST GAS CLEANING CATALYST USING THE SAME
JP2001129402A (en) * 1999-08-20 2001-05-15 Mitsubishi Motors Corp Catalyst for purifying exhaust gas
JP2001149757A (en) * 1999-11-29 2001-06-05 Cataler Corp Exhaust gas purifying catalyst

Also Published As

Publication number Publication date
EP1264629B1 (en) 2004-10-27
US6770590B2 (en) 2004-08-03
KR100464715B1 (en) 2005-01-06
EP1264629A1 (en) 2002-12-11
DE60201707T2 (en) 2005-03-10
JP2002361094A (en) 2002-12-17
US20030008773A1 (en) 2003-01-09
KR20020095079A (en) 2002-12-20
DE60201707D1 (en) 2004-12-02

Similar Documents

Publication Publication Date Title
US6729125B2 (en) Exhaust gas purifying system
KR100426517B1 (en) Exhaust gas purifying catalyst
US8569201B2 (en) Exhaust gas purifying catalyst and method for manufacturing the same
US6557342B2 (en) Exhaust gas purifying system
JP4645786B2 (en) Exhaust gas purification catalyst
WO2009144568A1 (en) Exhaust purification catalyst
KR100520250B1 (en) A catalysis for purify exhaust
US20110118113A1 (en) Exhaust gas purifying catalyst
JP4573993B2 (en) Exhaust gas purification catalyst and method for producing the same
EP1281437B1 (en) Catalyst for exhaust gas purification
JP3589383B2 (en) Exhaust gas purification catalyst
JP2004275814A (en) Exhaust gas purifying catalyst, its manufacturing method and exhaust gas purifying apparatus
JP2004216224A (en) Nox occlusion reduction type catalyst
JP4539809B2 (en) Exhaust purification device
JP3882884B2 (en) Exhaust gas purification catalyst
JP4503314B2 (en) Exhaust gas purification catalyst
JP7228451B2 (en) Exhaust gas purification catalyst for automobiles
JP3925013B2 (en) Exhaust gas purification device
JP3882885B2 (en) Exhaust gas purification catalyst
JP3885376B2 (en) Exhaust gas purification catalyst and method of using the same
JP4504307B2 (en) Exhaust gas purification device and exhaust gas purification catalyst for internal combustion engine
JP3855252B2 (en) Exhaust gas purification catalyst
JP2005238168A (en) Exhaust gas purification catalyst and apparatus for internal combustion engine
JP2005185965A (en) Exhaust gas purifying catalyst
JPH10128122A (en) Exhaust gas purifying catalyst and purification of exhaust gas

Legal Events

Date Code Title Description
A621 Written request for application examination

Free format text: JAPANESE INTERMEDIATE CODE: A621

Effective date: 20071219

A977 Report on retrieval

Free format text: JAPANESE INTERMEDIATE CODE: A971007

Effective date: 20100428

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20100512

A521 Written amendment

Free format text: JAPANESE INTERMEDIATE CODE: A523

Effective date: 20100622

TRDD Decision of grant or rejection written
A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

Effective date: 20101110

A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

A61 First payment of annual fees (during grant procedure)

Free format text: JAPANESE INTERMEDIATE CODE: A61

Effective date: 20101123

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20131217

Year of fee payment: 3

R151 Written notification of patent or utility model registration

Ref document number: 4645786

Country of ref document: JP

Free format text: JAPANESE INTERMEDIATE CODE: R151

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20131217

Year of fee payment: 3

EXPY Cancellation because of completion of term